1. Field of Invention
The invention relates to a motherboard and the control method thereof. In particular, the invention relates to a motherboard that can reset the CPU and the control method thereof.
2. Related Art
The central processing units (CPU) of computers have evolved from the 8086, 80286, 80386, and 80486 series in the early days to the modern Pentium 4 series, rendering more and better functions, computing speeds, and processing efficiency. With powerful functions and increasing data processing amount, the system has to perform more actions during the power on procedure to ensure the proper functioning of the CPU.
Take the Pentium 4 series CPU as an example. The motherboard has to send out a CPU_reset signal to the CPU during the boot power on self test (POST) in order to reset the CPU and to set the frequency multiplier of the CPU. The frequency multiplier refers to the ratio between the frequencies of the CPU and the system bus. When the external frequency is fixed, increasing the frequency multiplier will increase the main frequency of the CPU.
With reference to FIG. 1, the conventional way of resetting the CPU is achieved by an external reset from a south-bridge chipset 11. When the south-bridge chipset 11 performs the reset, a peripheral connecting interface reset (PCI_reset) signal S1 is generated. The PCI_reset signal is transmitted to a north-bridge chipset 12 to reset the north-bridge chipset 12. When north-bridge chipset 12 performs the reset, a CPU reset (CPU_reset) signal S2 is transmitted to the CPU 13 to reset the CPU 13.
However, aside from resetting the CPU 13 in the above-mentioned method, the north-bridge chipset 12 and the south-bridge chipset 11 are reset too. Therefore, it takes extra time to rewrite the data in the north-bridge chipset 12 and the south-bridge chipset 11.
Consequently, how to avoid writing the data required by the north-bridge chipset and the south-bridge chipset when resetting the CPU for saving time is currently an important issue.